1. Field of the Invention
The invention relates to rotatable couplings of the kind which are adapted by the inclusion of a flexible member to dampen vibrations and so prevent the transmission thereof unabated to mechanism driven through the coupling.
2. Description of the Prior Art
The power source for a sewing machine is commonly a series commutator motor which is fed from a supply of alternating current, and controlled with a solid state rectifier circuit of the type disclosed in U.S. Pat. No. Re. 25,203, for "Motor Control Circuit" issued July 24, 1962. Excellent speed control is obtainable with circuitry of the kind indicated, however, harsh pulses are experienced due to the chopped nature of the electrical wave form, and considerable noise is generated in the machine as a result.
It is a prime object of the present invention to reduce noise in a sewing machine due to rapid accelerations and decelerations of the motor drive shaft as occasioned by the operation of motor control circuitry.
It is another object of the invention to provide a flexible coupling in which the spring rate is variable in a manner enabling the coupling to substantially reduce input noise and vibration in mechanism driven by a motor acting through the coupling.
Other objects and advantages of the invention will become apparent during a reading of the specification taken in connection with the accompanying drawings.